The present invention relates to a table feeder apparatus for reciprocating a table equipped in a machine tool. Conventionally, such a type of table feeder has a feed screw such as a ball screw, and a feed nut engaging with the feed screw. While the feed screw is rotated by a motor around its axis, the feed nut integrally mounts thereon a block, which is directly attached to the table. Further, respective guide rails are disposed on the left and right sides transversely of the feed screw for guiding the table in the axial direction of the feed screw. The table has a guide piece which is engaged slideably on a guide face of each guide rail. Such a type of table feeder is operated to reciprocate the table together with the feed nut and the block in the axial direction of the feed screw, by rotating the feed screw through the motor.
However, in the conventional table feeder apparatus, the table is directly attached to the block as noted above, and the table receives through the block a subsidiary force in response to angular deflection of the feed nut. The guide rail is deformed by such a deflective force so that the table suffers from deviation due to the angular deflection of the feed nut. This occurs in the case that a surface of the guide rail has a relatively low rigidity even though the guide rail surface is worked precisely to secure its straight shape as accurate as possible. Therefore, linearity of the displacement of the table (hereinafter, "displacement linearity") is degraded, thereby failing to reciprocate the table accurately.
Conventionally, in order to ensure the displacement linearity of the table, the guide rail is enlarged to increase rigidity of the guide surface. However, an overall dimension of a machine is limited to a practical size, hence the guide rail cannot be enlarged unusually over a certain limit. Therefore, particularly in the case of utilizing a long and thick feed screw in the conventional table feeder having a compact size table, the guide rail may be deformed by the deflective force so that the table tends to deviate in response to the angular deflection of the feed nut to thereby degrade the displacement linearity of the table, due to various structural factors such as excessive rigidity of the thick feed screw, bending of the long feed screw, small dimension of the guide rail and poor rigidity of the thin table.